Earth has been taken over by a benign group of aliens known as the Monitors, gentlemanly figures clad in black overcoats and bowler hats. They are dedicated to suppressing humanity’s propensities for violence, sex, war, and trouble, enforcing their ethos with spray cans of a pacifying gas and with television ads praising the Monitors’ rule—the latter featuring cameos by a variety of comedic actors, as well as bandleader Xavier Cugat and Illinois senator Everett Dirksen (who died before the film’s release).
A conflict with the Monitors, inspired by the outrageous antics of a street preacher (Larry Storch), leads to the flight of movie actress Barbara (Susan Oliver), who is a collaborator with the Monitors, along with free-lance pilot Harry (Guy Stockwell) and Harry’s brother Max (Avery Schreiber), and their spiriting away by the “preacher”, who turns out to be a leader of SCRAG or “Secret Counter Retalitorial Group”, an anti-Monitor resistance group. After a series of vicissitudes, with Harry among the Monitors and Barbara and Max among the SCRAG forces, the principals are reunited and, minus Barbara, fly off to Washington, D.C., in an attempt to foil a SCRAG plot to bomb Monitor headquarters.
The Monitors, who have been aware of all these events, have decided that human beings are not worthy of their leadership, and they depart. Humanity is free to return to its violent and corrupt ways.